Shuttle assembly for tray handling

ABSTRACT

A shuttle assembly for handling trays of IC packages. The shuttle assembly is configured to accept cooperatively-configured trays in a vertically-extending tray stack volume in only a single rotational orientation. Trays are selectively released from or accepted by the tray stack volume by operation of selectively extendable and retractable tray support elements driven by actuators, which may comprise air cylinders. A lift mechanism for raising and lowering a tray in alignment with the tray stack volume may be included. A method of operation of the shuttle assembly is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. application Ser. Nos. 09/217,040,09/217,032, 09/217,029 and 09/217,039, all pending, by the sameinventors and filed on even date herewith.

BACKGROUND OF THE INVENTION

This invention relates generally to handling of semiconductor dicebearing integrated circuits (ICs) and, more specifically, to a shuttleassembly for handling trays configured to carry such dice in largegroups.

Since the first packaged integrated circuits (ICs) became commerciallyavailable, manufacturers have often found it necessary to identifypackaged ICs by marking each IC or packaged assembly of ICs with themanufacturer's name, a part or serial number, or other identifyinginformation such as a lot number or a wafer and/or die location. As themajority of ICs are packaged individually in a transfer-molded filledpolymer compound, most current marking systems have been developed forthis type of IC packaging.

Manufacturers initially marked packaged ICs using mechanical inktransferring devices, such as stamps or rollers, with or withoutstencils, to transfer ink to the surface of an IC. One example of anink-marking apparatus is disclosed in U.S. Pat. No. 5,226,361 to Grantet al. Because of the mechanical nature of the process and the dryingtime associated with ink, ink stamping systems are relatively slow andthe applied ink susceptible to smudging. Also, the quality ofink-stamped marks on packaged ICs can vary substantially over time andfrom IC to IC due to variations in the quality and quantity of inkapplied, ambient temperature and humidity, and the condition and finishof the surface of the stamp and the package.

Because of the deficiencies associated with ink stamping, manufacturershave in recent years switched to using a laser beam to mark the surfaceof a packaged IC. Unlike ink stamping, laser marking is very fast,requires no curing time, produces a consistently high quality mark, andcan take place at any point in the manufacturing process.

Various machines and methods have been developed for marking ICs with alaser. As illustrated in U.S. Pat. No. 5,357,077 to Tsuruta, U.S. Pat.No. 4,945,204 to Nakamura et al., U.S. Pat. No. 4,638,144 to Latta, Jr.,and U.S. Pat. No. 4,375,025 to Carlson, a packaged IC is placed in aposition where a laser beam, such as that produced by a carbon dioxideor neodymium-yttrium-aluminum garnet laser, inscribes various charactersor other information on a package surface. The laser beam bums away asmall amount of material on the surface of the IC package so that thearea where the characters are to appear has a different reflectivityfrom the rest of the package surface. By holding the packaged IC at aproper angle to a light source, the characters inscribed on the deviceby the laser can be read.

U.S. patent application Ser. No. 08/590,919 filed Jan. 24, 1996 now U.S.Pat. No. 5,937,270 by one of the present inventors, assigned to theassignee of the present invention and hereby incorporated herein by thisreference, discloses yet another laser marking system which is operableat high throughput volumes and makes substantially constant use of amarking laser by use of a multi-track IC feed, marking and inspectionprocedure. While highly successful, the laser marking system of the '919application feeds singulated, packaged ICs from tubular magazines alongtwo parallel, inclined tracks to a marking zone, after which the markeddevices are then automatically inspected and either discarded orreloaded into other tubular magazines at the output ends of the tracks.

Recently developed IC packages, however, are now much-reduced in size,thickness and dimensions of individual features, such as leads forexternal connection to higher-level packaging. One example of suchstate-of-the-art IC packages is a thin plastic package configurationidentified as a Thin Small Outline Package, or TSOP. Another is a ThinQuad Flat Pack, or TQFP. By way of comparison, such packages aredimensioned with a total package thickness, excluding lead fingers, ofless than about one-half the thickness of a conventional plastic SmallOutline J-lead package, or SOJ, such as would be marked in theabove-described system of the '919 application. These newer IC packages,with their smaller dimensions and more fragile components, are much moresusceptible to inadvertent damage in handling than prior package designsand, at best, are only marginally robust enough for handling in tubularmagazines and by singulated feed-through processing equipment. As aresult, the industry has gravitated to processing such relativelydelicate IC packages in batches carried in recesses of rectangulartrays, one example of which is so-called JEDEC trays. Other, evensmaller IC packages under current development and most recentlyintroduced to the market include so-called “chip scale” IC packages.These packages, having dimensions approximating those of a bare IC dieitself and employing extremely minute external connection elements, alsoare desirably handled in trays. It is contemplated that such chip scalepackages may be desirably laser marked on the bare, or thinly coated,backside of the die itself in instances where packaging is largelyintended to protect and seal the active surface at the die sides andprimarily extends over the sides and active (front) surface of the die.Accordingly, as used herein, the terms “IC package”, “packaged IC” or“IC” include not only conventional polymer-encapsulated dice but anydice incorporating sufficient structure to effect operative connectionto a higher level package such as a circuit card, or to another die.

In addition to the aforementioned difficulties with marking thin,reduced-dimension IC packages using tubular magazines and inclinedtracks, feeding and marking singulated IC packages, even when groupedfor marking, are time-consuming and fraught with potential for workpiecejamming somewhere on the tracks. Further, such an approach requiresnumerous sensors to verify passage of individual IC packages, locationof individual IC packages for marking and inspection, and counting of ICpackages to ensure full output magazines, but not magazine overfillingand jamming of the handling equipment for same. Further, movable stopsare required to locate and release the IC packages at numerous locationsand so, along with the proliferation of sensors, necessitate a somewhatcomplex and relatively expensive control apparatus for reliable systemoperation.

Another disadvantage of conventional laser marking systems lies in asafety requirement that the IC packages be enclosed in a laserlight-secure enclosure to prevent injury to personnel from the laserbeam. Such conventional laser marking systems employ a workpiece pathextending in a single plane through the marking station, thus requiringmovable access shutters which must be manipulated, resulting inadditional system cost and reducing throughput due to the time lost inopening and closing the shutters for entry and exit of groups of ICpackages as well as adding another timed operation to the sequence ofevents in the marking process.

While trays facilitate moving large batches of packaged ICs whileminimizing the risk of physical damage from handling, a problem withusing trays to carry IC packages for marking is the need to deal with awide range of tray-to-part tolerances. Thus, it would be necessary toorient the IC packages in the tray recesses to a common corner of eachtray pocket to obtain a repeatable marking of all the IC packages in thetray. It is also necessary to ensure that trays are received forhandling and processing in a proper orientation so that the IC packagesthemselves are properly oriented.

Accordingly, there is a need in the art for a mechanically andelectrically straightforward tray handling apparatus which provideshigh, reliable throughput.

BRIEF SUMMARY OF THE INVENTION

The present invention includes a shuttle assembly providing input andoutput tray singulation, pin one and part in tray verification as wellas proper, consistent tray orientation and thus proper IC packageorientation for IC packages carried in a tray.

In one embodiment, the present invention includes a shuttle assemblysuitable for delivering trays to, or receiving trays from, a transport.The shuttle assembly is configured to manipulate trays in a verticallystacked arrangement through the use of a frame defining a rectangulartray stack volume and supporting a tray support element initiatorproximate each corner of the tray stack volume. The frame includes aplurality of frame members configured and arranged to permit only asingle, proper, rotational orientation of trays placed in the tray stackvolume. The tray support element initiators may be controlled in common,each initiator driving a tray support element which may be spring-biasedtoward an extended position intersecting a boundary of the tray stackvolume. When a stack of trays is supported proximate its corners bylocation of the extended tray support elements under a lowermost tray,it may be removed from the shuttle assembly by extension of a liftstructure of a lift mechanism into supporting contact under thelowermost tray, whereupon the tray support elements may be retracted,the tray stack lowered the depth or thickness of one tray, the traysupport elements re-extended, and the lift structure with lowermost trayfurther lowered onto a tray carrier for horizontal movement by atransport actuator out from under the tray stack. Similarly, when a traycarrier bearing a tray enters a tray stack volume of a shuttle assembly,the tray may be lifted from the tray carrier into supporting contactwith a lowermost tray of a stack by extension of a lift structure of alift mechanism, the tray support elements retracted and the tray carrierwith supported stack of trays lifted the depth or thickness of a singletray, the tray support elements then being re-extended to support all ofthe trays of the stack.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 of the drawings comprises a perspective view of a laser markingsystem according to one embodiment of the present invention;

FIG. 2 comprises an enlargement of a central portion of FIG. 1;

FIG. 3 is an enlarged perspective view of a tray shuttle according toone embodiment of the present invention;

FIGS. 4-6 are side elevations of the tray shuttle assembly of FIG. 3 invarious positions;

FIGS. 7-9 are side, partial sectional elevations of a wedge-type liftmechanism according to one embodiment of the present invention invarious positions;

FIG. 10 is a top perspective view of a tray carrier and cooperating traytransport according to one embodiment of the present invention;

FIG. 11 is a vertically exploded view of FIG. 10;

FIG. 12 is a bottom, exploded perspective view of the tray carrier andcooperating tray transport of FIG. 10;

FIG. 13 is a perspective view of a tray carrier and cooperating traytransport of the present invention in a position for tilting of the traycarrier with respect to the tray transport;

FIG. 14 is a perspective view of the tray carrier of FIG. 13, tiltedwith respect to the tray transport;

FIG. 15 is a side elevation of a laser marking station with doorless aenclosure according to one embodiment of the present invention and alift mechanism according to the invention positioned to lift a traycarrier into the enclosure;

FIG. 16 is an enlarged side elevation of the apparatus depicted in FIG.15 with the tray carrier lifted into the enclosure of the laser markingstation to effect complete light containment in cooperation therewith;

FIGS. 17A-D are schematic representations of tray input cycle positionsof a wedge-type lift mechanism according to one embodiment of theinvention; and

FIGS. 18A-D are schematic representations of tray output cycle positionsof a wedge-type lift mechanism according to one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1 and 2 of the drawings, laser marking system 10includes an input shuttle assembly 12, an output shuttle assembly 14 anda transport actuator 16 extending horizontally therebetween. Thetransport actuator 16 extends under laser marking station 18. Three liftmechanisms 20 are located respectively in vertical alignment with inputshuttle assembly 12, laser marking station 18, and output shuttleassembly 14.

A plurality of vertically stacked trays 200 is depicted at both inputshuttle assembly assembly 12 and output shuttle assembly 14, thestructure and operation of each shuttle being described in more detailbelow. Also depicted (see FIG. 2) is tray carrier 22, on which asingulated tray 200 carrying a plurality of packaged ICs 202 (alsoreferred to as IC packages) in a rectangular array of recesses 204 (onlysome shown for clarity) comprising rows and columns may be moved on atray transport 24 (see FIGS. 4-8) of transport actuator 16 from inputshuttle assembly 12 to output shuttle assembly 14. Tray transport 24 maybe precisely rotationally aligned with the longitudinal path defined bytransport actuator 16 using Allen-type T-nuts, which secure traytransport 24 to the carriage of transport actuator 16.

A downwardly aimed inspection camera 30, as shown on the upstream sideof laser marking station 18, may be employed to verify pin one locationand thus proper orientation for the packaged ICs 202 in a tray 200passing thereunder on tray carrier 22, as well as part in trayverification to ensure that each tray 200 is fully loaded with packagedICs 202 for marking. A similar camera 30 on the downstream side of lasermarking station 18 may be employed to verify the presence of lasermarkings on each packaged IC 202 of a tray 200 which has been processedin laser marking station 18. A tray 200 is preferably stopped twice (andmoved a half-tray length between stops) under downstream camera 30 formark inspection, as packaged ICs 202 in each longitudinal half of eachtray 200 are substantially concurrently marked in a separate laser fieldby a different, separately (different circuit) controlled laser head oflaser marking station 18. Most preferably, marking of the last ICpackage in each field is checked on the logical premise thatsatisfactory marking of the last package would not take place if anyfailure in the laser or beam control circuitry had previously occurred.This sampling approach to inspection achieves the required qualityassurance for the marking process with a substantial time savings overinspecting every marked IC package. High-intensity lights (not shown)may be provided at the two camera locations to facilitate inspection.

Transport actuator 16 preferably comprises an IAI Corporation Model12EX-35-100 Intelligent Actuator, a 1000 mm programmable stepper.Transport actuator 16 may be programmed (by way of example only and notlimitation) for use with laser marking system 10 to six (6) positions:tray input, tray check (pin one location and tray full loadverification), marking, dual mark check (one for each half of the tray,as described above) and tray output. This particular approach totransporting a tray carrier 22 was selected due to the preciselongitudinal positional accuracy provided at each position. Other,alternative approaches to tray transport providing equivalent positionalaccuracy may be employed instead.

Input shuttle assembly 12 and output shuttle assembly 14 as depicted inFIGS. 1 and 2 are substantially identical. FIG. 3 shows an enlargementof the portion of FIG. 2 depicting input shuttle assembly 12, and withtransport actuator 16 removed for clarity. Input shuttle assembly 12includes a frame 40 comprising four frame members 42 a-d, each having avertically extending notch 44 facing a rectangular tray stack volume 46shown in broken lines. Frame members 42 a and 42 b extend upwardly agreater distance than frame members 42 c and 42 d, and define theuppermost preferred vertical height limit for a stack of trays 200, twoof which trays 200 being shown. As can readily be seen in FIG. 3, adistance or depth from a corner of tray stack volume 46 defined by anotch 44 to a laterally inward edge of each of frame members 42 a and 42c is smaller than a distance or depth from a corner of tray stack volume46 defined by a notch 44 to a laterally inward edge of each of framemembers 42 b and 42 d. Further, there is a laterally extending gap 43between frame members 42 a and 42 b and a like-sized gap 43 betweenframe members 42 c and 42 d. Protrusions 201 at each end of trays 200are sized and located on each end of the trays 200 to lie within gaps 43when a tray 200 is located in tray stack volume 46 so that the inputshuttle assembly 12 is “keyed” to only accept trays 200 in the properrotational orientation. In other words, the frame will not accept a tray200 placed “backward” in tray stack volume 46. Thus, the packaged ICs202 in each tray 200 will be in a proper orientation for marking. Eachframe member 42 a-d supports a tray support element actuator 47 on aheight-adjustable bracket 48. Tray support element actuators 47preferably comprise air (pneumatic) cylinders which, when actuated,retract a tab-like tray support element 50 which is otherwisespring-biased inwardly to intersect a boundary of tray stack volume 46,the tray support elements 50 each being located in their extendedpositions to enter one of four downwardly facing notches 206 in the side208 of a tray 200 proximate a tray corner 210. Thus, one or more trays200 may be supported at four locations within tray stack volume 46.Further, if air pressure to tray support element actuators 47 is lost,any trays 200 within tray stack volume 46 above tray support elements 50are kept from falling. Tray support element actuators 47 may compriseMyotoku Ltd. TKY-H-8X4 air cylinders. Tray carrier 22 is depicted undertray stack volume 46 in FIG. 3 in position to receive a tray 200 loweredthereon. FIGS. 4-6 depict a tray unload sequence, wherein (FIG. 4) atray transport 24 bearing a tray carrier 22 is located initially undertray stack volume 46 of input shuttle assembly 12 out of contact withlowermost tray 200, and parallel side plates 80 of a lift structure 78(FIG. 5) of a wedge-type lift mechanism 60, as described below, arevertically extended through elongated side notches 132 of tray carrier22 to supportingly engage the bottom of lowermost tray 200 and supportall of the trays in tray stack volume 46. At this point, tray supportelement actuators 47 are initiated to withdraw tray support elements 50.In FIG. 5, lowermost tray 200 has been lowered on side plates 80 of liftstructure 78 a vertical distance (for example, 0.25 inch) equal to thethickness of each tray 200, tray support element actuators 47deactivated to extend tray support elements 50 into downwardly-facingnotches 206 of the next highest tray 200, and then lowermost tray 200further lowered onto tray carrier 22. Tray carrier 22 carrying lowermosttray 200 is then moved horizontally out from under tray stack volume 46on tray carrier 22 and tray transport 24, as shown in FIG. 6, and towardlaser marking station 18.

In unloading trays 200 from tray carrier 22 at output shuttle assembly14 after passage through laser marking station 18, side plates 80 of alift structure 78 of a wedge-type lift mechanism 60 are verticallyextended through elongated side notches 132 of a tray carrier 22 alignedwith the tray stack volume 46 of output shuttle assembly 14 and carryinga tray 200 of marked packaged ICs 202 to raise that tray 200 intosupporting contact with a lowermost (or only) tray 200 already in traystack volume 46 and supported by tray support elements 50 of outputshuttle assembly 14. Tray support element actuators 47 are theninitiated to retract tray support elements 50, the stack of trays 200lifted the thickness of one tray 200 (again, for example, 0.25 inch),and tray support element actuators 47 deactivated to extend tray supportelements 50 into downwardly facing notches 206 of the lowermost tray 200just lifted from tray carrier 22 and support the stack of trays 200. Ofcourse, if there are no trays at output shuttle assembly 14 when a traycarrier 22 bearing a tray 200 arrives, the sequence will be the same.After side plates 80 are vertically withdrawn below the level of traycarrier 22 on tray transport 24, tray carrier 22 is returned on traytransport 24 to input shuttle assembly 12 to receive another tray 200 ofunmarked packaged ICs 202.

A significant feature of the laser marking system 10 is a particularwedge-type lift mechanism 60 (located as noted by reference numerals 20on the previously referenced drawing figures) as depicted in variouspositions in FIGS. 7-9. In the preferred embodiment, lift mechanism 60is employed with input shuttle assembly 12, output shuttle assembly 14and laser marking station 18. Lift mechanism 60 includes a horizontallyoriented stop dual-action (i.e., positive bidirectional actuation) aircylinder 62, which may comprise a Parker Series S pneumatic cylinder.Shaft 64 of cylinder 62 is extendable and retractable under air pressureto selectively provide a stop for dual-action, pneumatically actuateddrive block 66 riding on dual parallel horizontal guide shafts 68. Drivewedge element 70 carried on drive block 66 and secured thereto has anupper inclined surface 72 upon which is supported lower inclined surface74 of slave wedge element 76. Slave wedge element 76 is constrainedagainst horizontal movement by attachment to a three-sided liftstructure 78 comprising vertically-extending side plates 80 andhorizontal floor 82, side plates 80 being contained and guided by linearbearings 86 so as to permit only vertical movement. As drive block 66moves horizontally, such movement is translated into vertical movementof the lift structure 78 by movement of the inclined upper surface 72 ofdrive wedge element 70 against lower inclined surface 74 of slave wedgeelement 76. Due to the angle of inclination of surfaces 72 and 74,horizontal motion results in reduced vertical motion (by, for example, a4:1 horizontal to vertical ratio) but increased force over the smallervertical distance as well as a smoother vertical movement of liftstructure 78, reducing any shock of contact of lift structure 78 with atray 200. Furthermore, the control system for the lift mechanism 60,since it involves control of only two dual-action air cylinders, isextremely simple compared to conventional stepper or servo controls. Inthe preferred embodiment, the lift mechanism 60 with air cylinder 62 anddrive block 66 may be manipulated to move in a vertical increment equalto the thickness of trays 200, as alluded to above. Such manipulation ispossible due to the difference in travel between shaft 64 of aircylinder 62, which may be either three inches or one inch in thedisclosed embodiment as explained further below, and drive block 66,which is four inches in the disclosed embodiment. Further, air cylinder62 is sized to generate substantially more force than drive block 66, sothat actuation of air cylinder 62 in opposition to drive block 66precludes further movement of drive block 66 upon contact with shaft 64.Stated alternatively, the shaft 64 of air cylinder 62 may be selectivelyextended to act as a stop to fill horizontal travel of drive block 66and thus provide lift mechanism 60 with a vertical position betweenfully extended and fully retracted.

The uppermost vertical position of lift structure 78 of the liftmechanism 60 may obviously be designed in light of the level to which atray 200 must be lifted. For example, when used with both input shuttleassembly 12 and output shuttle assembly 14, the uppermost verticalposition of lift structure 78 (in this instance, 1.00 inch elevation)would be in supporting contact with the lowermost tray 200 in tray stackvolume 46. When used with input shuttle assembly 12, the uppermostvertical position is used to supportingly engage the lowermost tray intray stack volume 46 and support it to permit retraction of tray supportelements 50. When used with output shuttle assembly 14, the uppermostvertical position of lift structure 78 would be the same (1.00 inch) asfor input shuttle assembly 12, that is, one tray thickness (i.e., 0.25inch) higher than the bottom of the lowermost tray 200 in the tray stackvolume, so that a tray 200 full of marked IC packages 202 may be raisedinto lifting contact with the lowermost tray of a stack (or, statedanother way, so that notches 206 of the tray 200 being lifted by thelift structure 78 are above the tray support elements 50) so that thetray 200 being lifted from the tray carrier 22 (and trays 200 thereabovein the stack) may be supported by extended tray support elements 50.Thus, tray transport 24 with tray carrier 22 may be returned to inputshuttle assembly 12 to receive another tray 200. When used with lasermarking station 18, the uppermost vertical position of lift structure 78is also the same (1.00 inch) and is employed to place a tray 200 on traycarrier 22 within a substantially bottomless, laser light safeenclosure, as will be described in more detail below.

As shown in FIGS. 7-9 with specific reference to a lift mechanism for aninput shuttle assembly 12, lift mechanism 60 as described may beprogrammed to one of several vertical positions over a total travel of1.00 inch, including a zero elevation position wherein lift structure 78is completely retracted out of contact with a tray 200 when the latterrests on tray carrier 22 on tray transport 24 carried by transportactuator 16. For example, and with specific reference to FIG. 7, thelowermost vertical position of lift mechanism 60 (and therefore of liftstructure 78) is achieved when air cylinder 62 is actuated to withdrawshaft 64 to the left, as shown in the drawing figure, while drive block66 is similarly moved to the left so that slave wedge element 76 issubstantially superimposed over drive wedge element 70. In order toraise lift structure 78 to its uppermost vertical position as shown inFIG. 8 to, for example, receive a tray 200 from input shuttle assembly12, drive block 66 is actuated to move its full horizontal travel (fourinches) to the right, yielding 1.00 inch of lift travel. At the sametime, or subsequently, air cylinder 62 may be actuated to drive shaft 64its full horizontal travel (three inches) to the right in preparationfor the next movement sequence of lift mechanism 60. After tray 200 atthe bottom of a tray stack in input shuttle assembly 12 is contacted byside plates 80 of lift structure 78 and tray support elements 50retracted as previously described, drive block 66 is positively actuatedto move to the left. However, contact with extended shaft 64 of aircylinder 62, as shown in FIG. 9, prevents further, leftward movement ofdrive block 66, resulting in a downward vertical movement of liftstructure 78 of only 0.25 inch (one inch of horizontal travel of driveblock 66 being reduced by a 1 to 4 ratio due to the angle of inclinationof like-angled inclined surfaces 72 and 74) to a 0.75 inch elevation. Atthis point, tray support elements 50 are again extended to support thenext-lowermost tray 200 in the stack, as shown in FIG. 5, and aircylinder 62 may then be actuated to positively drive shaft 64 to theleft, followed by leftward movement of already-actuated drive block 66to return lift structure 78 to its lowermost position, as shown in FIG.7. A complete tray input cycle sequence of positions of drive wedgeelement 70, slave wedge element 76, shaft 64 and drive block 66 of awedge-type lift mechanism 60 usable with an input shuttle assembly 12according to one embodiment of the present invention is schematicallydepicted in FIGS. 17A-17D. Lift mechanism 60 moves from its lowermostposition (FIG. 17A) to its uppermost elevation of 1.00 inch (FIG. 17B),moves downward 0.25 inch to a 0.75 inch elevation (FIG. 17C) and thenmoves back to its lowermost position (FIG. 17D).

It should be noted that, while the elements of wedge-type lift mechanism60 are the same when used with both input shuttle assembly 12 and outputshuttle assembly 14, air cylinder 62 is reversed in orientation due tospace considerations and the travel of shaft 64 extending therefrom isabbreviated, as explained further below.

When lift mechanism 60 is employed with output shuttle assembly 14, theinitial raised position of lift structure 78 is at 0.75 inch, whereinthe bottom of a stack of trays 200 is contacted in supportingrelationship by a tray 200 of marked IC packages 202. Then, tray supportelements 50 are retracted to permit lift structure 78 movement to fullvertical travel of 1.00 inch to lift the tray stack upwardly one traythickness so that tray support elements 50 may be extended to supportthe stack by the newly-added lowermost tray 200 just received from traycarrier 22. A complete tray output cycle sequence of positions of drivewedge element 70, slave wedge element 76, shaft 64 and drive block 66 ofa wedge-type lift mechanism 60 usable with an output shuttle assembly14, according to one embodiment of the present invention, isschematically depicted in FIGS. 18A-18D. As depicted in FIGS. 18A-18D,when used with an output shuttle assembly 14, the lift mechanism 60moves from a lowermost position (FIG. 18A) to a 0.75 inch elevationposition (FIG. 18B), wherein drive block 66 has moved from left toright, but its travel has been halted by contact with extended shaft 64′of air cylinder 62, in this instance, placed to the right of drive block66 rather than to the left. Since shaft 64′, when extended, only travelsone inch, the travel of drive block 66 to the right is halted at the0.75 inch elevation of lift mechanism 60. Shaft 64′ is then retracted tothe right, followed by drive block 66, causing lift mechanism 60 toreach its full vertical travel of 1.00 inch (FIG. 18C). Drive block 66is then moved to the left (FIG. 18D).

It may be desirable to include sensors in lift mechanism 60 to detectpositions of drive block 66 and shaft 64 or 64′. For example, driveblock position may be sensed using magnetic proximity sensors, while theextension or retraction of shaft 64 or 64′ may be inductively sensed.Other types of sensors, for example, optical sensors or contactswitches, might also be employed in this capacity.

In use with laser marking station 18, only drive block 66 is required inlift mechanism 60, since only two vertical positions are required. Thefirst position of lift structure 78 corresponds to that shown in FIG. 7,while the second, full vertical extension position of lift structure 78corresponds to that shown in FIG. 8. The second position extends a traycarrier 22 bearing a tray 200 into enclosure 120 (FIGS. 1, 2, 15, and16) of laser marking station 18 as will be more fully described below.

Yet another significant feature (see FIGS. 10-12) is a self-aligning,cooperative configuration of tray carrier 22 and tray transport 24 toensure repeatable, precise positioning of a tray 200 borne by the traycarrier 22 with respect to input and output tray stack volumes 46 andlaser marking station 18. As noted previously, tray carrier 22 is liftedoff of tray transport 24 by a lift structure 78 into the substantiallybottomless enclosure 120 of laser marking station 18 and then returnedtherefrom for transport to output shuttle assembly 14. It is imperativethat tray carrier 22 be in a precise location and position when liftedfrom tray transport 24 and that it be returned to the same, preciselocation for reliable tray movement, to maintain the integrity of partson the tray, and to ensure trouble-free operation when unloading andloading trays 200 at shuttle assemblies 12 and 14. This preciseorientational requirement, moreover, must be accommodated withoutphysical connection of the tray carrier 22 to tray transport 24.Therefore, the substantially planar lower surface 90 of tray carrier 22is provided with a plurality of hemispherical recesses 92 which are oflike radius and in the same positions as hemispherical bearings 94projecting upwardly from substantially planar upper surface 96 of traytransport 24. This cooperative recess and bearing configuration providesrobust, repeatable, gravity-enhanced alignment when the two componentsare mated.

Referring to FIG. 12 of the drawings, the reader will note the presenceof an additional hemispherical recess 98 on lower surface 90 of traycarrier 22 offset from the four hemispherical recesses 92. Additionalrecess 98, when used with a longitudinally foreshortened (in comparisonto tray carrier 22) tray transport 24 as shown in FIGS. 11-14, permitsthe tilting of a tray 200 on tray carrier 22 (constrained againstmovement, of course, by corner stops 100 extending upwardly fromsubstantially planar upper surface 101 of tray carrier 22) by verticalextension of a shaft 102 of an air cylinder (not shown), shaft 102 beingsurmounted by a bearing cylinder supporting a spherical bearing 104 oflike radius to bearings 94 and aligned with additional recess 98. Thetwo recesses 92 most distant from, and diagonally located with respectto, additional recess 98, engaged by their cooperating bearings 94 oftray transport 24, provide a tilt pivot point or fulcrum for tilting oftray carrier 22 and the tray 200 residing therein at an angle to thelongitudinal axis of the normally superimposed tray carrier 22 and traytransport 24, such tilting being further facilitated by diagonaltruncation or cutout 106 of the nearby corner of tray transport 24.Tilting results in movement of each IC package 202 in a tray borne bythe tray carrier 22 toward the same corner of the tray recess 204 (FIG.2) in which that IC package 202 is located. Also noteworthy in FIGS. 13and 14 is the presence of part movement facilitator 110, which maycomprise a vibrator, or an air cylinder actuated to “tap” the traycarrier 22 repeatedly to overcome any sliding friction preventing the ICpackages from moving to their desired positions. The tray tiltinglocation (with optional part movement facilitator 110) may be at theposition of tray transport 24 under the laser marking station 18 toeffect precise alignment of IC packages 202 immediately before markingor may be located at the upstream side of laser marking station 18 wheretray carrier 22 passes under inspection camera 30, so that the positionof each IC package 202 may be checked.

Yet another significant feature of the laser marking system of thepresent invention is the configuration of laser marking station 18.Specifically, laser marking station 18 employs a substantiallybottomless enclosure 120 having four sides and a roof (see FIGS. 1, 2,15 and 16) which, unlike conventional marking stations previouslyreferenced herein, does not require opening and closing of accessshutters to admit a group of IC packages to be marked. Instead, a tray200 of unmarked IC packages 202 positioned below enclosure 120 as shownin FIG. 15 and residing on carrier tray 22, which in turn rests on traytransport 24 of transport actuator 16 (not shown in FIGS. 15 and 16 forclarity), may be raised off of tray transport 24 into the opening 122defined in the bottom of enclosure 120 when contacted by parallelextensions 124 at the tops of side plates 80 of lift structure 78, theupper ends 126 of extensions 124 including notched edges 128 bracketinga central protrusion 130 sized and located to closely fit withinelongated side notches 132 of tray carrier 22. As shown in FIGS. 10-14,the lateral extent or width of tray transport 24 is less than that oftray carrier 22 so that side plates 80 pass outboard of tray transport24 before extensions 124 engage elongated side notches 132 of traycarrier 22. As shown in FIG. 16, when lift structure 78 of liftmechanism 60 is fully vertically extended, tray carrier 22 issubstantially contained within enclosure 120 and the tray 200 is locatedcompletely within enclosure 120 at the proper focal length for lasermarking with the assurance that laser light emitted from the markingheads will be completely contained within enclosure 120. Further, traycarrier 22 is sized and shaped to act as a substantially light-tightclosure to bottom opening 122 of enclosure 120. Completion of theclosure is effected by the presence of extensions 124 in elongated sidenotches 132, extensions 124 being of adequate width to fill the width ofnotches 132. Assurance of a light-tight enclosure 120 may be furtherprovided with magnetic sensors on the interior of enclosure 120 whichwill confirm the proper location of tray carrier 22 in positionresponsive to the presence in the proper location within enclosure 120of two magnets 134 (FIGS. 10, 11, 13 and 14) secured in tray carrier 22.

It is preferred that two laser marking heads 140 under control ofseparate electronics and powered from a single laser output beam dividedby a beam splitter are focused on separate portions of a marking fieldwithin enclosure 120. Thus, a 6 inch by 12 inch marking field may bedefined, affording the capability to mark IC packages 202 of an entiretray 200 without tray movement. A suitable laser marking device is theModel 1900, offered by General Scanning. To further ensure properoperation of the laser marking system 10 and provide additionalassurance against premature actuation thereof, it may be appropriate toinclude sensors, such as optical or magnetic sensors, to sense thepresence of a tray 200 in the laser marking field.

With respect to the tray handling aspects of the invention, it may alsobe desirable to provide sensors to sense when tray output shuttleassembly 14 is full of trays 200 and when a tray 200 has cleared thelevel of tray support elements 50. Similarly, tray input shuttleassembly 12 may employ a tray presence sensor to confirm that a tray 200is, in fact, loaded onto tray carrier 22 and a stack presence sensor todetect when there are no more trays 200 present to be loaded onto traycarrier 22. Fiber optic reflection-type sensors are one exemplary sensortechnology which may be employed. In addition, such sensors may beemployed to sense the position of the air cylinder shafts 64 and driveblocks 66 of lift mechanisms 60.

While the present invention has been described in the context of anillustrated embodiment, those of ordinary skill in the art willrecognize and appreciate that it is not so limited. Specifically andwithout limitation, additions or modifications to, or deletions from,the apparatus of the invention and its operation as described may bemade without departing from the scope of the invention as defined by theclaims appended hereto. In addition, various elements and subassembliesof the overall system of the present invention as disclosed alsoindividually and in various combinations are included within the ambitof the present invention.

What is claimed is:
 1. A shuttle assembly for handling trays adapted tocarry a plurality of ICs therein, comprising: a frame defining avertical, substantially rectangular tray stack volume of like length andwidth dimensions to trays to be handled, the frame configured to accepttrays in the tray stack volume only in a single rotational orientation;and a plurality of tray support element actuators mounted to the frame,each tray support element actuator having a tray support elementextendable therefrom into the tray stack volume.
 2. The shuttle assemblyof claim 1, wherein the plurality of tray support element actuatorscomprise air cylinders.
 3. The shuttle assembly of claim 2, wherein thetray support elements are biased to extend into the tray stack volume.4. The shuttle assembly of claim 3, wherein the tray support elementsare biased by springs.
 5. The shuttle assembly of claim 4, wherein theframe comprises four frame members, each including a verticallyextending notch defining a corner of the tray stack volume, each of theframe members carrying a tray support element actuator of said pluralityof tray support element actuators.
 6. The shuttle assembly of claim 5,wherein the notches of two of the frame members differ in depth from thenotches of another two of the frame members, and the frame members arespaced so that, in combination with the differing notch depths, theframe is configured to receive trays in the tray stack volume in onlythe single rotational orientation.
 7. The shuttle assembly of claim 6,further including a vertically extendable and retractable lift mechanismdisposed under the tray stack volume.
 8. The shuttle assembly of claim7, wherein the lift mechanism is configured to place a tray at leastpartially above the tray support elements.
 9. The shuttle assembly ofclaim 8, wherein the lift mechanism is configured to place a traysubstantially one tray thickness below the placement at least partiallyabove the tray support elements.
 10. The shuttle assembly of claim 1,wherein the frame comprises four frame members, each including avertically extending notch defining a corner of the tray stack volume,each of the frame members carrying a tray support element actuator ofsaid plurality of tray support element actuators.
 11. The shuttleassembly of claim 10, wherein the notches of two of the frame membersdiffer in depth from the notches of another two of the frame members,and the frame members are spaced so that, in combination with thediffering notch depths, the frame is configured to receive trays in thetray stack volume in only the single rotational orientation.
 12. Theshuttle assembly of claim 11, further including a vertically extendableand retractable lift mechanism disposed under the tray stack volume. 13.The shuttle assembly of claim 12, wherein the lift mechanism isconfigured to place a tray at least partially above the tray supportelements.
 14. The shuttle assembly of claim 13, wherein the liftmechanism is configured to place a tray substantially one tray thicknessbelow the placement at least partially above the tray support elements.15. The shuttle assembly of claim 1, wherein the frame is configured tocooperatively engage a tray in the tray stack volume in only the singlerotational orientation.